三板溪面板堆石坝面板裂缝成因分析

采用钢筋应力计、无应力计、应变计、温度计、裂缝计等监测仪器对三板溪混凝土面板堆石坝进行监测,研究三板溪混凝土面板堆石坝在施工期和运行期的应力、变形分布规律,分析混凝土面板产生结构性裂缝的可能原因。监测资料分析结果表明:导致面板水平施工缝挤压破损的直接原因是面板水平缝缝面压应力过大和结构上的缺陷;从外部运行环境看,首次蓄水水位上升过快引起大坝变形速率过大,面板偏心受压,最终导致面板水平缝挤压破损。     

混凝土面板堆石坝面板裂缝成因及防治

混凝土面板堆石坝的面板裂缝一直是面板施工中的一个难题,如何优化面板混凝土设计与施工,减少裂缝的产生;如何有效地处理已产生的裂缝,对今后的面板混凝土设计与施工有着非常重要的意义。     

涔天河水库扩建工程一期混凝土面板裂缝处理效果分析

以涔天河水库扩建工程一期混凝土面板为例,采用岩石破裂过程分析软件((RFPA2D)模拟单裂缝分别在温胀和温缩荷载效应下的动态扩展过程,揭示混凝土面板裂缝形成的主要原因及影响因素,并采用钻孔取芯进行检测验证。结果表明,缩性裂缝形态特征与混凝土芯样裂缝较为一致,混凝土收缩(干缩和温缩)是产生裂缝的主要原因,刮涂聚脲和化学灌浆是处理混凝土面板裂缝有效措施。     

面板堆石坝分离式面板应力变形特性研究

为进一步研究分离式面板的技术特点,利用商业有限元分析软件ABAQUS分别对分离式和连续式面板堆石坝进行数值模拟,对满蓄期连续式面板和分离式面板的应力应变状态进行了对比分析。计算结果表明,相比于连续式面板,分离式素混凝土面板技术的应用改善了面板在满蓄期的应力分布状况,提高了混凝土面板对堆石体变形的适应能力;不同水平缝宽度对面板的整体应力应变状态影响较小,为避免局部应力过大而导致的混凝土挤压破坏,其宽度应根据变形计算进行确定。     

西藏楚松面板坝混凝土面板施工

楚松水库面板混凝土在高寒、干燥、温差较大的气候条件下施工,合理安排施工季节,严格控制混凝土的浇筑工艺和活水养护工作,是搞好混凝土质量,防止裂缝乃至大坝的长久安全运用的根本保证。     

水布垭大坝面板在强地震作用下的非线性有限元分析

采用非线性动态显式有限元方法,对清江水布垭面板堆石坝在地震作用下的动态响应进行了计算分析,指出了混凝土面板在地震波作用下的应力水平和应力分布特点,预测了混凝土面板在地震发生后的结构完整性,计算经果表明,地震波作用下该坝混凝土面板强度满足设计安全要求。     

混凝土面板裂逢的因素迭加分析——从乌鲁瓦提面板坝谈面板混凝土裂缝

根据观测成果,从混凝土自身因素、施工因素、温变因素、养护因素、基础约束因素等方面,详细全面地阐述了混凝土面板裂缝产生发展的原因,有助于解决面板裂缝这一难题并为类似问题提供参与.     

面板堆石坝面板的裂缝机理分析与防裂措施

面板作为面板堆石坝的挡水结构,在面板堆石坝设计中占有重要地位。混凝土面板裂缝一直是面板设计与施工中的一个难题。针对面板的裂缝问题,对面板结构性裂缝和非结构性裂缝的机理进行了分析,并列举了一些工程上常用的防止面板裂缝的措施。     

水布垭堆石坝混凝土面板施工技术创新

针对水布垭堆石坝的混凝土面板具有长度大、长宽比大、厚度较薄的结构特点,在面板施工过程中,通过堆石体施工期沉降变形控制、挤压边墙原材料与结构形式改进、混凝土面板浇筑施工三方面的技术创新与应用,攻克了高面板坝混凝土施工的重大技术难题,有效确保了水布垭堆石坝混凝土面板的各项性能,为坝体的稳定安全运行提供了保障,可供借鏊.     

200 m级面板堆石坝流变分析

针对堆石流变会引起200 m级面板堆石坝面板脱空、压坏等现象,采用沈珠江三参数流变模型对200m级混凝土面板堆石坝进行三维有限元计算,对比了不考虑堆石料流变的计算结果,并分析了堆石料流变特性对坝体和混凝土面板应力变形及面板接缝变形的影响.结果表明,堆石流变较大程度上改变了坝体和面板的变形与应力.     

西藏楚松混凝土面板砂卵石坝填筑工艺

西藏楚松混凝土面板砂卵石坝座落在寒冷缺氧的高原,昼夜温差大。利用了两段两期围堰导流;机械化开挖和运输筑坝,使用许多不同类型的材料;薄层填筑,由震动压路机碾压;填筑质量标准和检测用相对密度和干密度,取得成功经验。     

新疆山口电站堆石坝混凝土面板温度收缩应力分析及其防裂措施

山口水电站是以发电、灌溉效益为主的水利枢纽工程。山口电站面板堆石坝位于新疆北部高寒干旱地区，针对该区的气候特点对面板温度应力进行了详细的论证分析，提出了适宜的面板施工时间和可行有效的防裂措施。     

Effect of curing on positive-plate behaviour in electric scooter lead/acid cells

This study investigates how curing temperature affects the composition and material structure of lead/acid positive plates. According to experimental results, the major morphology in positive active-material crystals is tribasic lead sulfate ( = 3BS) at a low temperature and tetrabasic lead sulfate ( = 4BS) at a high curing temperature (> 65 °C). Obviously, different curing conditions influence heavily electrode composition and cell performance. A driving pattern is developed for an electric scooter (ES) driving pattern according to urban driving pattern conditions (CNS-D3029). Three groups of cells with different curing temperatures (45, 65 and 85 °C) are subjected to two test methods: standard cycle testing, and ES-driving pattern cycle testing. The results demonstrate that the plates cured at the higher temperature contain less initial capacity but have a longer cycle life under both test conditions.     

半导体封装快速养护炉炉温分布的计算机仿真

半导体封装快速养护炉是半导体封装过程中的一个关键设备。半导体封装粘结工艺养护过程要求炉内温度均匀分布，现有养护炉不能满足这一要求。通过对某养护炉炉内温度场的计算机仿真分析发现，现有养护炉在设计上存在缺陷，通过加长养护炉的方法，可以改善养护炉内温度场的分布，满足半导体封装粘结工艺养护的要求。     

燃气轮机调节方式对IGCC系统变工况性能的影响

为选择合理的燃气轮机调节方式,采用Thermoflex软件建立了200 MW级IGCC系统模型,从系统的角度出发比较研究了燃气轮机的调节方式对燃气顶循环系统、蒸汽底循环系统和整个IGCC系统变工况性能的影响.研究表明:与压气机可转导叶(IGV)不调相比,IGV可调时更有利于提高系统的变工况性能.等燃气透平初温(T3)调...     

Thermal characteristics of shape-stabilized phase change material wallboard with periodical outside temperature waves

Thermal characteristics of shape-stabilized phase change material (SSPCM) wallboard with sinusoidal temperature wave on the outer surface were investigated numerically and compared with traditional building materials such as brick, foam concrete and expanded polystyrene (EPS). One-dimensional enthalpy equation under convective boundary conditions was solved using fully implicit finite-difference scheme. The simulation results showed that the SSPCM wallboard presents distinct characteristics from other ordinary building materials. Phase transition keeping time of inner surface and decrement factor were applied to analyze the effects of PCM thermophysical properties (melting temperature, heat of fusion, phase transition zone and thermal conductivity), inner surface convective heat transfer coefficient and thickness of SSPCM wallboard. It was found that melting temperature is one important factor which influences both the phase transition keeping time and the decrement factor; for a certain outside temperature wave, there exist critical values of latent heat of fusion and thickness of SSPCM above which the phase transition keeping time or the decrement factor are scarcely influenced; thermal conductivity of PCM and inner surface convective coefficient have little effect on the phase transition keeping time but significantly influence the decrement factor; and the phase transition zone leads to small fluctuations of the original flat segment of inner surface temperature line. The results aim to be useful for the selection of SSPCMs and their applications in passive solar buildings.     

On Investigating the Thermomechanical Properties of Cross-linked Epoxy Via Molecular Dynamics Analysis

In this work, we demonstrate the feasibility of a computational approach based on first principles for estimating various thermomechanical quantities of a cross-linked epoxy resin. In particular, this work is focused on determining estimated values of the variation in glass transition temperature, coefficient of thermal expansion, volume shrinkage due to curing, Young’s modulus, Poisson’s ratio, yield strength, and viscosity as a function of temperature and degree of curing via molecular dynamics simulations. In most cases it has been demonstrated that the values predicted by the proposed approach are in good agreement with the respective experimentally measured values. In addition, the validity of the proposed models describing the dependence of the thermomechanical quantities on temperature and curing degree is examined. Throughout this study, we demonstrate that the molecular dynamics–based computational predictive framework can serve as an excellent infrastructure that can enable numerical prediction of materials properties and thereby can reduce the costs of associated with physical experimentation. In addition, we demonstrate that insightful information can be generated at the molecular and microscopic scales that is not easily extractable from experiments.     

高层节能住宅外墙外保温施工浅谈

阐述了高层建筑外墙外保温的发展方向简况,介绍了一种全新的外墙外保温体系－将钢丝网聚苯板放置于外墙外板内侧墙体浇注混凝土时一次成型的外保温墙体,阐述了保温板、墙体热工性能、施工工艺以及防止抹灰裂缝措施等方面的情况．